This is the summer of the supermoon, with three full moons in a row that appear bigger and brighter than normal. But this weekend marks the year's most super-duper supermoon: When the moon rises on Sunday evening, it'll be as close as a full moon ever gets to Earth during 2014.
Purists will protest: At its closest, the full moon is about 14 percent wider and 30 percent brighter than it is at its farthest. That difference is virtually impossible to perceive with the naked eye. It becomes noticeable only when you compare two photos of the full moon taken under the same conditions at different times of year.
What's more, the moon comes as close if not closer every month. What makes Sunday's moon so super is merely the fact that this month's lunar perigee (221,796 miles at 1:46 p.m. ET) occurs at around the same time as the official moment of the moon's full phase (2:09 p.m. ET).
Despite what the purists might say, Supermoon Sunday provides a fine excuse to look at the moon and the night sky, which is something most of us don't do enough. Even observers in light-polluted locales like New York City can make out the moon — in fact, last month's supermoon was a co-star in New York's Manhattanhenge double-header.
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One strategy for supermoon-watching would be to take in the experience around midnight, when your viewing location is at its minimum distance from the moon. But to maximize the drama, stake out a spot with a clear view to the east, and watch for the moon creeping up into the sky around sunset. This online calculator from TimeandDate.com can tell you when moonrise occurs in your area, and the Clear Sky Chart shows the forecasts for sky conditions.
It's well-known that the moon looks bigger when it's near the horizon than when it's high in the sky, although there's some debate about the reason for the perceptual "moon illusion." Some say it's because our brain is wired to compare the size of the rising moon with terrestrial objects at the horizon — or it may be because of the way we perceive clouds as they move from the horizon to directly overhead.
Whatever the reason, the moon looks more impressive when it's on the rise. And it also makes for a better picture when you can include something interesting in the foreground of your supermoon snapshot. Like the French Alps, for instance.
If the skies are cloudy all night on Sunday, keep two things in mind. First, the moon will be almost as big and bright on Monday (or on Saturday, for that matter). Second, the Slooh virtual observatory is planning an online moon-watching party starting at 7:30 p.m. ET Sunday. The show airs via Slooh's website as well as Livestream.com.
You'll be able to watch live streaming video of what Slooh calls the "Mega-Moon" from various locations in North America, with commentary by Slooh's Bob Berman and Paul Cox. There'll also be recorded coverage of the night's moonrise from Dubai, Australia and other locations around the globe. Viewers can ask questions during the show by tweeting with the hashtag #SloohMegaMoon.
"Nothing in the sky is more striking than the rising of an enormous-looking full moon," Berman said in a news release. "And this will be largest since March 2011."
There's one super-duper downside to the supermoon: It's coming at just the wrong time for the Perseid meteor shower, which hits its annual peak around Aug. 11 to 13. During that time frame, the glare of the just-past-full moon will overwhelm the shooting stars virtually all night.
The Perseids occur every August when Earth passes through the stream of cosmic grit left behind by Comet Swift-Tuttle. When the viewing conditions are at their best, skywatchers could see scores of meteors in the course of an hour. This year, there's a chance of spotting the brightest fireballs, but not much else.
The best time to look for meteors would be soon after sunset, when the moon is still low in the east — or just before sunrise, when the moon is low in the west. You can make things easier by positioning yourself in a "moonshadow," where the moon's disk is hidden from sight.
Slooh has scheduled online coverage of the Perseids starting at 7 p.m. ET Tuesday, featuring live views from the Institute of Astrophysics in the Canary Islands. There'll also be recorded video segments about meteors, and viewers can ask questions during the show by using the hashtag #PerseidsSloohsation.
If the Perseids are a washout, don't be dismayed — make a note to take in the Orionids in October or the Leonids in November, when the moon won't be so intrusive. And if it's any consolation, the Perseids should be perfect in 2015.